Toward Efficient and Stable Perovskite Solar Cells by 2D Interface Energy Band Alignment

Interfacial engineering is essential for facilitating carrier separation, charge extraction, and enhancing the stability in organic–inorganic perovskite solar cells (PSCs). Herein, a facile and effective method is demonstrated not only to tune the electronic performance of electron transporting layer (ETL) but also to passivate the defects at the interface between the ETL and perovskite. On the top of the tin(IV) oxide (SnO₂) ETL, butylammonium chloride (BACl) and lead(II) iodide (PbI₂) are introduced as interface to modify the ETL/perovskite interface. The PSCs with interface modified exhibit a power conversion efficiency (PCE) of 21.15%, compared to 18.33% for the device without interface modified. Such enhancement in efficiency is mainly attributed to a better energy band alignment, and the quality of perovskite films is improved through the interface modification, thus enhancing photogenerated charge extraction and leading to low charge carrier recombination at the interface of ETL/perovskite. Furthermore, the device with interface modified exhibits significant stability. This work provides an alternative strategy on the ETL/perovskite interface to obtain highly stable and efficient PSCs.